1. Field of the Invention
The present invention relates, in general, to a clamping jig and system for inspecting spacer grids for a nuclear fuel assembly which is capable of firmly and precisely clamping a variety of spacer grids on a measurement stage moving at high speed so that, among constituent parts of the nuclear fuel assembly, the spacer grids can be inspected using a non-contact measurer.
2. Description of the Related Art
In general, spacer grids used to support and fix fuel rods are interwoven grid straps having springs and dimples in rows and columns, and are welded at the intersections of the grid straps.
In spacer grids that are currently in use, inner and outer grid straps are arranged in rows and columns to form cells which accept fuel rods, and the arranged grid straps are fused by laser welding or brazing. Each cell of the spacer grid includes springs and dimples formed on its faces to support a fuel rod. Positions and shapes of the springs and dimples have a great influence on the performance of nuclear fuel rod assembly.
Currently, at least 20 types of spacer grids are produced, depending on the type of nuclear reactor core, the method of fusion of the spacer grid, and the function of the spacer grid. In the process of producing the spacer grid, the dimension and shape of the spring and dimple of the spacer grid can vary as a result of external impact and/or high temperatures generated by grid strap fusion. To determine if undesirable variations have occurred, the spacer grid must be inspected.
To inspect the spacer grid, the verticality of the dimple and a distance between the dimple and the spring are measured using a non-contact, three-dimensional inspection system. Here, a jig capable of firmly clamping the spacer grid is required. Existing jigs, however, can clamp only a specific type or size of spacer grid. Thus, only one spacer grid can be mounted and measured at a time, and therefore, it is impossible to avoid costly extended inspection time and reduced inspection efficiency.